Method of manufacture of a thermoelastic bend actuator using PTFE and corrugated copper ink jet printer

ABSTRACT

A method of manufacturing an ink jet printhead the method including the step of depositing a sacrificial material on a substrate and etching the sacrificial material to form a plurality of ink chambers on the substrate, with each ink chamber having an ink ejection port. A thermal expansion material and a conductive material are deposited and etched to form a thermal actuator in each ink chamber. Each thermal actuator comprises an electrical heater element of the conductive material, positioned in the thermal expansion material, the thermal expansion material having a coefficient of thermal expansion which is such that the thermal expansion material is capable of expansion upon heating by the electrical heater element. The heater element is positioned in the thermal material so that such expansion of the thermal expansion material results in displacement of the thermal actuator with respect to the ink ejection port.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

CROSS-REFERENCED U.S. PATENT/ AUSTRALIAN PATENT APPLICATION PROVISIONAL(CLAIMING RIGHT OF PATENT PRIORITY FROM AUSTRALIAN DOCKET APPLICATIONNO. PROVISIONAL APPLICATION) NO. PO7991 09/113,060 ART01 PO850509/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO801709/112,747 ART06 PO8014 09/112,776, PN 6227648 ART07 PO8025 09/112,750ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742ART11 PO8031 09/112,741 ART12 PO8030 09/112,740, PN 6196541 ART13 PO799709/112,739, PN 6195150 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO8018 09/112,777ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO8024 09/112,805ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 09/112,797,PN 6137500 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO802209/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO802309/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO797709/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO849909/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO798609/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO802709/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO939609/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO9399 6,106,147 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO940209/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP095909/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP237109/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02PO9404 09/113,101 Fluid03 PO8066 09/112,751, PN 6227652 IJ01 PO807209/112,787, PN 6213588 IJ02 PO8040 09/112,802, PN 6213589 IJ03 PO807109/112,803, PN 6231163 IJ04 PO8047 09/113,097, PN 6247795 IJ05 PO803509/113,099 IJ06 PO8044 09/113,084, PN 6244691 IJ07 PO8063 09/113,066, PN6257704 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779, PN 6220694 IJ10PO8069 09/113,077, PN 6257705 IJ11 PO8049 09/113,061, PN 6247794 IJ12PO8036 09/112,818, PN 6234610 IJ13 PO8048 09/112,816, PN 6247793 IJ14PO8070 09/112,772, PN 6264306 IJ15 PO8067 09/112,819, PN 6241342 IJ16PO8001 09/112,815, PN 6247792 IJ17 PO8038 09/113,096, PN 6264307 IJ18PO8033 09/113,068, PN 6259220 IJ19 PO8002 09/113,095, PN 6234611 IJ20PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780, PN5239821 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121, PN 6247796 IJ25PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756, PN6227653 IJ31 PO9391 09/112,755, PN 6234609 IJ32 PP0888 09/112,754, PN6238040 IJ33 PP0891 09/112,811, PN 6188415 IJ34 PP0890 09/112,812, PN6227654 IJ35 PP0873 09/112,813, PN 6209989 IJ36 PP0993 09/112,814, PN6247791 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765, PN 6217153 IJ39PP2592 09/112,767 IJ40 PP2593 09/112,768, PN 6243113 IJ41 PP399109/112,807, PN 6283581 IJ42 PP3987 09/112,806, PN 6247790 IJ43 PP398509/112,820, PN 6260953 IJ44 PP3983 09/112,821, PN 6267469 IJ45 PO793509/112,822, PN 6224780 IJM01 PO7936 09/112,825, PN 6235212 IJM02 PO793709/112,826, PN 6280643 IJM03 PO8061 09/112,827, PN 6284147 IJM04 PO805409/112,828, PN 6214244 IJM05 PO8065  6,071,750 IJM06 PO8055 09/113,108,PN 6267905 IJM07 PO8053 09/113,109, PN 6251298 IJM08 PO8078 09/113,123,PN 6258285 IJM09 PO7933 09/113,114, PN 6225138 IJM10 PO7950 09/113,115IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125,PN 6231773 IJM14 PO8073 09/113,126, PN 6190931 IJM15 PO8076 09/113,119IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221, PN 6241906 IJM18 PO805009/113,116 IJM19 PO8052 09/113,118, PN 6241905 IJM20 PO7948 09/113,117IJM21 PO7951 09/113,113, PN 6231772 IJM22 PO8074 09/113,130, PN 6274056IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112, PN 6248248 IJM25 PO805809/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045  6,111,754 IJM28 PO795209/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769, PN 6264849IJM31 PO9392 09/112,770, PN 6254793 IJM32 PP0889 09/112,798, PN 6235211IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800, PN 6264850 IJM37 PP087409/112,799, PN 6258284 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833,PN 6228668 IJM40 PP2591 09/112,832, PN 6180427 IJM41 PP3990 09/112,831,PN 6171875 IJM42 PP3986 09/112,830, PN 6267904 IJM43 PP3984 09/112,836,PN 6245247 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102, PN 6231148IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085, PN6238111 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP087709/112,760 IR16 PP0878 09/112,773, PN 6196739 IR17 PP0879 09/112,774IR18 PP0883 09/112,775, PN 6270182 IR19 PP0880 09/112,745, PN 6152619IR20 PP0881 09/113,092 IR21 PO8006  6,087,638 MEMS02 PO8007 09/113,093MEMS03 PO8008 09/113,062 MEMS04 PO8010  6,041,600 MEMS05 PO801109/113,082 MEMS06 PO7947  6,067,797 MEMS07 PO7944 09/113,080 MEMS09PO7946  6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the manufacture of ink jet printheadsand, in particular, discloses a method of manufacture of an ink jetprinthead.

BACKGROUND OF THE INVENTION

Many ink jet printing mechanisms are known. Unfortunately, in massproduction techniques, the production of ink jet printheads is quitedifficult. For example, often, the orifice or nozzle plate isconstructed separately from the ink supply and ink ejection mechanismand bonded to the mechanism at a later stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)). The separate material processing stepsrequired in handling such precision devices often add a substantialexpense to manufacturing.

Additionally, side shooting ink jet technologies (U.S. Pat. No.4,899,181) are often used but again, this limits the amount of massproduction throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilized. Thesecan include electroforming of nickel (Hewlett-Packard Journal, Vol. 36no 5, pp33-37 (1985)), electro-discharge machining, laser ablation (U.S.Pat. No. 5,208,604), micro-punching, etc.

The utilization of the above techniques is likely to add substantialexpense to the mass production of ink jet printheads and therefore addsubstantially to their final cost.

It would therefore be desirable if an efficient system for the massproduction of ink jet printheads could be developed.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there isprovided a method of manufacturing an ink jet printhead having athermoelastic bend actuator using polytetrafluoroethylene (PTFE) andcorrugated copper wherein an array of nozzles are formed on a substrateutilizing planar monolithic deposition, lithographic and etchingprocesses. Preferably, multiple ink jet printheads are formedsimultaneously on a single planar substrate such as a silicon wafer.

The printheads can be formed utilizing standard vlsi/ulsi processing andcan include integrated drive electronics formed on the same substrate.The drive electronics are preferably of a CMOS type. In the finalconstruction, ink can be ejected from the substrate substantially normalto the surface of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic cross-sectional view of a single ink jet nozzle ofan ink jet printhead constructed in accordance with the preferredembodiment;

FIG. 2 is a schematic cross-sectional view of the single ink jet nozzle,with a thermal actuator in an activated state;

FIG. 3 is a schematic diagram of a conductive layer utilized in thethermal actuator of the ink jet nozzle;

FIG. 4 is a close-up perspective view of portion A of FIG. 3;

FIG. 5 is a cross-sectional schematic diagram illustrating theconstruction of a corrugated the conductive layer in accordance with thepreferred embodiment of the present invention;

FIG. 6 is a schematic cross-sectional diagram illustrating thedevelopment of a resist material through a half-toned mask utilized inthe fabrication of a single ink jet nozzle in accordance with thepreferred embodiment;

FIG. 7 is an exploded perspective view illustrating the construction ofa single ink jet nozzle in accordance with the preferred embodiment;

FIG. 8 is a perspective view of a section of an ink jet printheadconfiguration utilizing ink jet nozzles constructed in accordance withthe preferred embodiment.

FIG. 9 provides a legend of the materials indicated in FIG. 10 to 23;and

FIG. 10 shows a wafer in a first step of a manufacturing process of theinvention;

FIG. 11 shows the wafer of FIG. 10 with an etched sacrificial layerdefining venting layer support posts and an anchor point;

FIG. 12 shows the wafer of FIG. 11 with edges of a venting layer;

FIG. 13 shows the wafer of FIG. 12 with an actuator anchor point;

FIG. 14 shows the wafer of FIG. 13 etched to receive a heater layer;

FIG. 15 shows the wafer of FIG. 14 with deposited heater material;

FIG. 16 shows the wafer of FIG. 15 with a sacrificial layer etched foran actuator paddle and bond pads;

FIG. 17 shows the wafer of FIG. 16 with a sacrificial layer etched for anozzle chamber;

FIG. 18 shows the wafer of FIG. 17 with PECVD glass deposited thereon;

FIG. 19 shows the wafer of FIG. 18 etched for a nozzle rim;

FIG. 20 shows the wafer of FIG. 19 with a sacrificial layer etched todefine an ink ejection port;

FIG. 21 shows the wafer of FIG. 20 with channels etched through thewafer;

FIG. 22 shows the wafer of FIG. 21 with nozzle chambers cleared andactuators freed; and

FIG. 23 shows a nozzle filled with ink.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In FIG. 1, there is illustrated a cross-sectional view of a singleinkjet nozzle 10 constructed in accordance with the present embodiment.The inkjet nozzle 10 includes an ink ejection port 11 for the ejectionof ink from a chamber 12 by the actuation of a thermal paddle actuator13. The thermal paddle actuator 13 comprises an inner copper heatingportion 14 and a panel 15 which are encased in an outer PTFE layer 16.The outer PTFE layer 16 has an extremely high coefficient of thermalexpansion (approximately 770×10⁻⁶, or around 380 times that of silicon).The PTFE layer 16 is also highly hydrophobic which results in an airbubble 17 being formed under the actuator 13 due to out-gassing etc. Thetop PTFE layer is treated so as to make it hydrophilic. The heater 14 isalso formed within the lower portion of the actuator 13.

The heater 14 is connected at ends 20,21 (see also FIG. 7) to a lowerCMOS drive layer 18 containing drive circuitry (not shown). For thepurposes of actuation of the actuator 13, a current is passed throughthe copper heater element 14 which heats the bottom surface of theactuator 13. Turning now to FIG. 2, the bottom surface of the actuator13, in contact with the air bubble 17 remains heated while any topsurface heating is carried away by the exposure of the top surface ofthe actuator 13 to the ink within the chamber 12. Hence, the bottom PTFElayer expands more rapidly resulting in a generally rapid upward bendingof the actuator 13 (as illustrated in FIG. 2) which causes the ejectionof ink from the ink ejection port 11. An air inlet channel 28 is formedbetween two nitride layers 42, 26 such that air is free to flow in adirection indicated by an arrow 29 along channel 28 and through holes25, in accordance with any fluctuating pressure influences. The air flow29 acts to reduce the vacuum on the back surface of the actuator 13during operation. As a result less energy is required for the movementof the actuator 13.

The actuator 13 can be deactivated by turning off the current to theheater element 14. This will result in a return of the actuator 13 toits rest position.

The actuator 13 includes a number of significant features. In FIG. 3there is illustrated a schematic diagram of a conductive layer of thethermal actuator 13. The conductive layer includes the panel 15, whichcan be constructed from the same material as the heater 14 copper, andwhich contains a series of holes 23. The holes are provided forinterconnecting layers of PTFE both above and below the panel 15 so asto resist any movement of the PTFE layers past the panel 15 and therebyreducing any opportunities for the delamination of the PTFE and copperlayers.

Turning to FIG. 4, there is illustrated a close up view of a portion ofthe actuator 13 of FIG. 1 illustrating the corrugations 22 of the heaterelement 14 within the PTFE of the actuator 13 of FIG. 1. The corrugation22 of the heater 14 allow for a rapid heating of the portions of thebottom layer surrounding the heater 14. Any resistive heater which isbased upon applying a current to heat an object will result in a rapid,substantially uniform elevation in temperature of the outer surface ofthe current carrying conductor. The surrounding PTFE volume is thereforeheated by means of thermal conduction from the heater 14. This thermalconduction is known to proceed, to a first approximation, at asubstantially linear rate with respect to distance from a resistiveelement. By utilizing the corrugations 22 the bottom surface of theactuator 13 is more rapidly heated as, the bottom PTFE surface is closerto the heater 14. Therefore, the utilization of the corrugations 22results in a more rapid heating of the bottom surface layer andtherefore a more rapid actuation of the actuator 13. Further, thecorrugations 22 also assist in resisting any delamination of the copperand the PTFE layers.

Turning now to FIG. 5, the heater 14 can be formed by depositing aresist layer 50 on top of the first PTFE layer 51. The resist layer 50is exposed utilizing a mask 52 having a half-tone pattern delineatingthe corrugations 22. After development the resist 50 contains acorrugation pattern. The resist layer 50 and the PTFE layer 51 are thenetched utilizing an etchant that erodes the resist layer 50 atsubstantially the same rate as the PTFE layer 51. This transfers thecorrugated pattern into the PTFE layer 51. Turning to FIG. 6, on top ofthe corrugated PTFE layer 51 is deposited the copper heater layer 14which takes on a corrugated form in accordance with its under layer. Thecopper heater layer 14 is then etched in a serpentine or concertinaform. Subsequently, a further PTFE layer 53 is deposited on top of thelayer 14 to form the top layer of the thermal actuator 13. Finally, thesecond PTFE layer 52 is planarized to form the top surface of thethermal actuator 13 (FIG. 1).

Returning again now to FIG. 1, it is noted that an ink supply can besupplied through a channel 38 which can be constructed by means of deepanisotropic silicon trench etching such as that available from STSLimited (“Advanced Silicon Etching Using High Density Plasmas” by J. K.Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings inMicro Machining and Micro Fabrication Process Technology). The inksupply flows from the channel 38 through spaced apart apertures 40 (seealso FIG. 7) into chamber 12. The apertures 40 are defined between poles241, forming a filter 341 (see FIG. 7). Importantly, the poles 241 whichcan comprise silicon nitride or similar insulating material act toremove foreign bodies from the ink flow. The poles 241 also help topinch the PTFE actuator 13 to a base CMOS layer 18, the pinchingproviding an important assistance for the thermal actuator 13 so as toensure a substantially decreased likelihood of the thermal actuatorlayer 13 separating from a base CMOS layer 18.

A series of sacrificial etchant holes 19 are provided in the top wall 48of the chamber 12 to allow sacrificial etchant to enter the chamber 12during fabrication so as to increase the rate of etching. The small sizeof the holes 19 does not affect the operation of the device 10substantially as the surface tension across the holes 19 stops ink frombeing ejected from these holes 19, whereas the larger size port 11allows for the ejection of ink.

Turning now to FIG. 7, there is illustrated an exploded perspective viewof the nozzle 10. The nozzles 10 can be formed in layers starting with asilicon wafer substrate 41 having a CMOS layer 18 on top thereof asrequired. The CMOS layer 18 provides the various drive circuitry fordriving the copper heater 14.

A nitride layer 42 is deposited on top of the CMOS layer 18, providingprimarily protection for lower layers from corrosion or etching. Next aPTFE layer 26 is constructed having the aforementioned holes 25 (seeFIG. 1), and posts 27 (see FIG. 1). The structure of the PTFE layer 26can be formed by first laying down a sacrificial glass layer (not shown)onto which the PTFE layer 26 is deposited. The PTFE layer 26 includesvarious features, for example, a lower ridge portion 30 in addition tovias for the subsequent material layers.

In construction of the actuator 13 (FIG. 1), the process of creating afirst PTFE layer 60 proceeds by laying down a sacrificial layer on topof the layer 26 in which the air bubble 17 underneath the actuator 13(FIG. 1) subsequently forms. On top of this is deposited a first PTFElayer utilizing the relevant mask. Preferably, the PTFE layer includesvias for subsequent copper interconnections. Next, a copper layer 43 isdeposited on top of the first PTFE layer 60 and a subsequent PTFE layer61 is deposited on top of the copper layer 43, in each case, utilizingthe required mask.

The nitride layer 46 can be formed by using of a sacrificial glass layerwhich is masked and etched as required to form the side walls and thegrill 40. Subsequently, the top nitride layer 48 is deposited againutilizing the appropriate mask having the holes 19 as required.Subsequently, the various sacrificial layers are etched away so as torelease the structure of the thermal actuator 13.

In FIG. 8 there is illustrated a section of an ink jet printheadconfiguration 90 utilizing ink jet nozzles constructed in accordancewith the preferred embodiment shown at 91. The configuration 90 can beused in a three color process, 1600 dpi printhead having three sets oftwo rows of nozzle chambers 92,93, which are interconnected to one inksupply channel 94, for each set. Three supply channels 94, 95, 96 areinterconnected to cyan colored, magenta colored and yellow colored inkreservoirs respectively. Ink is supplied through respective apertures200, 202, 204 formed in the wafer substrate 206 and extending throughthe wafer substrate 206 to the back surface thereof.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed using thefollowing steps:

1. Using a double sided polished wafer 41, complete drive transistors,data distribution, and timing circuits using a 0.5 micron, one poly, 2metal CMOS process 18. Relevant features of the wafer at this step areshown in FIG. 10. For clarity, these diagrams may not be to scale, andmay not represent a cross section though any single plane of the nozzle.FIG. 9 is a key to representations of various materials in thesemanufacturing diagrams, and those of other cross referenced ink jetconfigurations.

2. Deposit 1 micron of low stress nitride 42. This acts as a barrier toprevent ink diffusion through the silicon dioxide of the chip surface.

3. Deposit 2 microns of sacrificial material 60 (e.g. polyimide).

4. Etch the sacrificial layer using Mask 1. This mask defines the PTFEventing layer support posts 27 and anchor point. This step is shown inFIG. 11.

5. Deposit 2 microns of PTFE 26.

6. Etch the PTFE using Mask 2. This mask defines the edges of the PTFEventing layer, and the holes 25 in this layer. This step is shown inFIG. 12.

7. Deposit 3 microns of sacrificial material 61 (e.g. polyimide).

8. Etch the sacrificial layer using Mask 3. This mask defines theactuator anchor point. This step is shown in FIG. 13.

9. Deposit 1 micron of PTFE 62.

10. Deposit, expose and develop 1 micron of resist using Mask 4. Thismask is a gray-scale mask which defines the heater vias 20, 21 as wellas the corrugated PTFE surface that on which the heater is subsequentlydeposited.

11. Etch the PTFE and resist at substantially the same rate. Thecorrugated resist thickness is transferred to the PTFE, and the PTFE iscompletely etched in the heater via positions. In the corrugatedregions, the resultant PTFE thickness nominally varies between 0.25micron and 0.75 micron, though exact values are not critical. This stepis shown in FIG. 14.

12. Deposit and pattern resist using Mask 5. This mask defines theheater.

13. Deposit 0.5 microns of gold 63 (or other heater material with a lowYoung's modulus) and strip the resist. Steps 12 and 13 form a lift-offprocess. This step is shown in FIG. 15.

14. Deposit 1.5 microns of PTFE 16.

15. Etch the PTFE down to the sacrificial layer using Mask 6. This maskdefines the actuator paddle and the bond pads. This step is shown inFIG. 16.

16. Wafer probe. All electrical connections are complete at this point,and the chips are not yet separated.

17. Plasma process the PTFE to make the top and side surfaces of thepaddle hydrophilic. This allows the nozzle chamber 12 to fill bycapillarity.

18. Deposit 10 microns of sacrificial material 64.

19. Etch the sacrificial material down to nitride using Mask 7. Thismask defines the nozzle chamber 12. This step is shown in FIG. 17.

20. Deposit 3 microns of PECVD glass 46. This step is shown in FIG. 18.

21. Etch to a depth of 1 micron using Mask 8. This mask defines thenozzle rim 65. This step is shown in FIG. 19.

22. Etch down to the sacrificial layer using Mask 9. This mask definesthe ejection port 11 and the sacrificial etch access holes 19. This stepis shown in FIG. 20.

23. Back-etch completely through the silicon wafer (with, for example,an ASE Advanced Silicon Etcher from Surface Technology Systems) usingMask 10. This mask defines the ink channels 38 which are etched throughthe wafer. The wafer is also diced by this etch. This step is shown inFIG. 21.

24. Back-etch the CMOS oxide layers and subsequently deposited nitridelayers and sacrificial layer through to PTFE using the back-etchedsilicon as a mask.

25. Etch the sacrificial material. The nozzle chambers 12 are cleared,the actuators 13 freed, and the chips are separated by this etch. Thisstep is shown in FIG. 22.

26. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink 66 to the ink inlets at the back of the wafer.

27. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

28. Hydrophobize the front surface of the printheads.

29. Fill the completed printheads with ink and test them. A fillednozzle is shown in FIG. 23.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademark of Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per print head, but is a majorimpediment to the fabrication of pagewidth print heads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the list under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems

For ease of manufacture using standard process equipment, the print headis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the print head is 100mm long, with a width which depends upon the ink jet type. The smallestprint head designed is Ser. No. 09/112,764, which is 0.35 mm wide,giving a chip area of 35 square mm. The print heads each contain 19,200nozzles plus data and control circuitry.

Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprint head is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

The present invention is useful in the field of digital printing, inparticular, ink jet printing. A number of patent applications in thisfield were filed simultaneously and incorporated by cross reference.

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. Forty-five such inkjet typeswere filed simultaneously to the present application.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the forty-five examples can be made intoink jet print heads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The simultaneously filed patent applications by the present applicantare listed by USSN numbers. In some cases, a print technology may belisted more than once in a table, where it shares characteristics withmore than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) DescriptionAdvantages Disadvantages Examples Thermal An electrothermal Large forceHigh power Canon Bubblejet bubble heater heats the ink to generated Inkcarrier 1979 Endo et al GB above boiling point, Simple limited to waterpatent 2,007,162 transferring significant construction Low efficiencyXerox heater-in- heat to the aqueous No moving parts High pit 1990Hawkins et ink. A bubble Fast operation temperatures al U.S. Pat. No.4,899,181 nucleates and quickly Small chip area required Hewlett-Packardforms, expelling the required for actuator High mechanical TIJ 1982Vaught et ink. stress al U.S. Pat. No. 4,490,728 The efficiency of theUnusual process is low, with materials required typically less thanLarge drive 0.05% of the electrical transistors energy being Cavitationcauses transformed into actuator failure kinetic energy of the Kogationreduces drop. bubble formation Large print heads are difficult tofabricate Piezo- A piezoelectric crystal Low power Very large area Kyseret al U.S. Pat. No. electric such as lead consumption required foractuator 3,946,398 lanthanum zirconate Many ink types Difficult toZoltan U.S. Pat. No. (PZT) is electrically can be used integrate with3,683,212 activated, and either Fast operation electronics 1973 Stemmeexpands, shears, or High efficiency High voltage U.S. Pat. No. 3,747,120bends to apply drive transistors Epson Stylus pressure to the ink,required Tektronix ejecting drops. Full pagewidth IJ04 print headsimpractical due to actuator size Requires electrical poling in highfield strengths during manufacture Electro- An electric field is Lowpower Low maximum Seiko Epson, strictive used to activate consumptionstrain (approx. Usui et all JP electrostriction in Many ink types 0.01%)253401/96 relaxor materials such can be used Large area IJ04 as leadlanthanum Low thermal required for actuator zirconate titanate expansiondue to low strain (PLZT) or lead Electric field Response speed magnesiumniobate strength required is marginal (˜10 (PMN). (approx. 3.5 V/μm) μs)can be generated High voltage without difficulty drive transistors Doesnot require required electrical poling Full pagewidth print headsimpractical due to actuator size Ferro- An electric field is Low powerDifficult to IJ04 electric used to induce a phase consumption integratewith transition between the Many ink types electronics antiferroelectric(AFE) can be used Unusual and ferroelectric (FE) Fast operationmaterials such as phase. Perovskite (<1 μs) PLZSnT are materials such astin Relatively high required modified lead longitudinal strain Actuatorsrequire lanthanum zirconate High efficiency a large area titanate(PLZSnT) Electric field exhibit large strains of strength of around 3 upto 1% associated V/μm can be readily with the AFE to FE provided phasetransition. Electro- Conductive plates are Low power Difficult to IJ02,IJ04 static plates separated by a consumption operate electrostaticcompressible or fluid Many ink types devices in an dielectric (usuallyair). can be used aqueous Upon application of a Fast operationenvironment voltage, the plates The electrostatic attract each other andactuator will displace ink, causing normally need to be drop ejection.The separated from the conductive plates may ink be in a comb or Verylarge area honeycomb structure, required to achieve or stacked toincrease high forces the surface area and High voltage therefore theforce. drive transistors may be required Full pagewidth print heads arenot competitive due to actuator size Electro- A strong electric fieldLow current High voltage 1989 Saito et al, static pull is applied to theink, consumption required U.S. Pat. No. 4,799,068 on ink whereupon Lowtemperature May be damaged 1989 Miura et al, electrostatic attraction bysparks due to air U.S. Pat. No. 4,810,954 accelerates the ink breakdownTone-jet towards the print Required field medium. strength increases asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent Au electromagnet Low powerComplex IJ07, IJ10 magnet directly attracts a consumption fabricationelectro- permanent magnet, Many ink types Permanent magnetic displacingink and can be used magnetic material causing drop ejection. Fastoperation such as Neodymium Rare earth magnets High efficiency IronBoron (NdFeB) with a field strength Easy extension required. around 1Tesla can be from single nozzles High local used. Examples are: topagewidth print currents required Samarium Cobalt heads Copper (SaCo)and magnetic metalization should materials in the be used for longneodymium iron boron electromigration family (NdFeB, lifetime and lowNdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usuallyinfeasible Operating temperature limited to the Curie temperature(around 540 K) Soft A solenoid induced a Low power Complex IJ01, IJ05,IJ08, magnetic magnetic field in a soft consumption fabrication IJ10,IJ12, IJ14, core electro- magnetic core or yoke Many ink types Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such Fast operation CMOS fab such as as electroplatediron High efficiency NiFe, CoNiFe, or alloys such as CoNiFe Easyextension CoFe are required [1], CoFe, or NiFe from single nozzles Highlocal alloys. Typically, the to pagewidth print currents required softmagnetic material heads Copper is in two parts, which metalizationshould are normally held be used for long apart by a spring.electromigration When the solenoid is lifetime and low actuated, the twoparts resistivity attract, displacing the Electroplating is ink.required High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06, IJ11, IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally to fromsingle nozzles High local the print head, for to pagewidth printcurrents required example with rare heads Copper earth permanentmetalization should magnets. be used for long Only the currentelectromigration carrying wire need be lifetime and low fabricated onthe print- resistivity head, simplifying Pigmented inks materials areusually requirements. infeasible Magneto- The actuator uses the Many inktypes Force acts as a Fischenbeck, striction giant magnetostrictive canbe used twisting motion U.S. Pat. No. 4,032,929 effect of materials Fastoperation Unusual IJ25 such as Terfenol-D (an Easy extension materialssuch as alloy of terbium, from single nozzles Terfenol-D are dysprosiumand iron to pagewidth print required developed at the Naval heads Highlocal Ordnance Laboratory, High force is currents required henceTer-Fe-NOL). available Copper For best efficiency, the metalizationshould actuator should be pre- be used for long stressed to approx. 8electromigration MPa. lifetime and low resistivity Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EPtension pressure is held in a consumption supplementary force 0771 658A2 and reduction nozzle by surface Simple to effect drop related patenttension. The surface construction separation applications tension of theink is No unusual Requires special reduced below the materials requiredin ink surfactants bubble threshold, fabrication Speed may be causingthe ink to High efficiency limited by surfactant egress from the Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are No unusual to effect drop related patentto be ejected. A materials required in separation applications viscosityreduction can fabrication Requires special be achieved Easy extensionink viscosity electrothermally with from single nozzles properties mostinks, but special to pagewidth print High speed is inks can beengineered heads difficult to achieve for a 100:1 viscosity Requiresreduction. oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is Canoperate Complex drive 1993 Hadimioglu generated and without a nozzlecircuitry et al, EUP 550,192 focussed upon the plate Complex 1993 Elrodet al, drop ejection region. fabrication EUP 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermo- An actuatorwhich Low power Efficient aqueous IJ03, IJ09, IJ17, elastic bend reliesupon differential consumption operation requires a IJ18, IJ19, IJ20,actuator thermal expansion Many ink types thermal insulator on IJ21,IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27,IJ28, used. Simple planar Corrosion IJ29, IJ30, IJ31, fabricationprevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35,IJ36, IJ37, required for each Pigmented inks IJ38, IJ39, IJ40, actuatormay be infeasible, IJ41 Fast operation as pigment particles Highefficiency may jam the bend CMOS actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a very Highforce can Requires special IJ09, IJ17, IJ18, thermo- high coefficient ofbe generated material (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermalexpansion Three methods of Requires a PTFE IJ23, IJ24, IJ27, actuator(CTE) such as PTFE deposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a with high conductive material is candidatefor low temperature (above incorporated. A 50 μm dielectric constant350° C.) processing long PTFE bend insulation in ULSI Pigmented inksactuator with Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conductive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such asVery low power development (High elastic PTFE) is doped with consumptionCTE conductive actuator conducting substances Many ink types polymer) toincrease its can be used Requires a PTFE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape. Lowvoltage High current The shape change operation operation causesejection of a Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic Linear Magnetic Requires unusual IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance Longactuator boron (NdFeB) Actuator (LSRA), and travel is available Requiresthe Linear Stepper Medium force is complex multi- Actuator (LSA).available phase drive circuitry Low voltage High current operationoperation

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesActuator This is the simplest Simple operation Drop repetition Thermalink jet directly mode of operation: the No external rate is usuallyPiezoelectric ink pushes ink actuator directly fields required limitedto around 10 jet supplies sufficient Satellite drops kHz. However, thisIJ01, IJ02, IJ03, kinetic energy to expel can be avoided if is notfundamental IJ04, IJ05, IJ06, the drop. The drop drop velocity is lessto the method, but is IJ07, IJ09, IJ11, must have a sufficient than 4m/s related to the refill IJ12, IJ14, IJ16, velocity to overcome Can beefficient, method normally IJ20, IJ22, IJ23, the surface tension.depending upon the used IJ24, IJ25, IJ26, actuator used All of the dropIJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32, be provided bythe IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, Satellite drops IJ39,IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44 velocity is greaterthan 4.5 m/s Proximity The drops to be Very simple print Requires closeSilverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced The drop the print media orapplications surface tension selection means transfer roller reductionof does not need to May require two pressurized ink). provide the energyprint heads printing Selected drops are required to separate alternaterows of the separated from the ink the drop from the image in the nozzleby nozzle Monolithic color contact with the print print heads are mediumor a transfer difficult roller. Electro- The drops to be Very simpleprint Requires very Silverbrook, EP static pull printed are selected byhead fabrication can high electrostatic 0771 658 A2 and on ink somemanner (e.g. be used field related patent thermally induced The dropElectrostatic field applications surface tension selection means forsmall nozzle Tone-Jet reduction of does not need to sizes is above airpressurized ink). provide the energy breakdown Selected drops arerequired to separate Electrostatic field separated from the ink the dropfrom the may attract dust in the nozzle by a nozzle strong electricfield. Magnetic The drops to be Very simple print Requires Silverbrook,EP pull on ink printed are selected by head fabrication can magnetic ink0771 658 A2 and some manner (e.g. be used Ink colors other relatedpatent thermally induced The drop than black are applications surfacetension selection means difficult reduction of does not need to Requiresvery pressurized ink). provide the energy high magnetic fields Selecteddrops are required to separate separated from the ink the drop from thein the nozzle by a nozzle strong magnetic field acting on the magneticink. Shutter The actuator moves a High speed (>50 Moving parts are IJ13,IJ17, IJ21 shutter to block ink kHz) operation can required flow to thenozzle. The be achieved due to Requires ink ink pressure is pulsedreduced refill time pressure modulator at a multiple of the Drop timingcan Friction and wear drop ejection be very accurate must be consideredfrequency. The actuator Stiction is energy can be very possible lowShuttered The actuator moves a Actuators with Moving parts are IJ08,IJ15, IJ18, grill shutter to block ink small travel can be required IJ19flow through a grill to used Requires ink the nozzle. The shutterActuators with pressure modulator movement need only small force can beFriction and wear be equal to the width used must be considered of thegrill holes. High speed (>50 Stiction is kHz) operation can possible beachieved Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an ‘ink energy operation is external pulsed pullon ink pusher’ at the drop possible magnetic field pusher ejectionfrequency. An No heat Requires special actuator controls a dissipationmaterials for both catch, which prevents problems the actuator and thethe ink pusher from ink pusher moving when a drop is Complex not to beejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly Simplicity of Dropejection Most ink jets, fires the ink drop, and construction energy mustbe including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03,size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, oscillator related patentacoustic ejection energy. The allowing higher Ink pressure applicationsstimul- actuator selects which operating speed phase and amplitude IJ08,IJ13, IJ15, ation) drops are to be fired The actuators must be carefullyIJ17, IJ18, IJ19, by selectively may operate with controlled IJ21blocking or enabling much lower energy Acoustic nozzles. The inkAcoustic lenses reflections in the ink pressure oscillation can be usedto focus chamber must be may be achieved by the sound on the designedfor vibrating the print nozzles head, or preferably by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP proximity placed in close High accuracy assembly required 0771 658 A2and proximity to the print Simple print head Paper fibers may relatedpatent medium. Selected construction cause problems applications dropsprotrude from Cannot print on the print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to a High accuracy Bulky Silverbrook, EP roller transfer rollerinstead Wide range of Expensive 0771 658 A2 and of straight to the printprint substrates can Complex related patent medium. A transfer be usedconstruction applications roller can also be used Ink can be driedTektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. ink jet Any of the lJ series Electro- Anelectric field is Low power Field strength Silverbrook, EP static usedto accelerate Simple print head required for 0771 658 A2 and selecteddrops towards construction separation of small related patent the printmedium. drops is near or applications above air Tone-Jet breakdownDirect A magnetic field is Low power Requires Silverbrook, EP magneticused to accelerate Simple print head magnetic ink 0771 658 A2 and fieldselected drops of construction Requires strong related patent magneticink towards magnetic field applications the print medium. Cross Theprint head is Does not require Requires external IJ06, IJ16 magneticplaced in a constant magnetic materials magnet field magnetic field. Theto be integrated in Current densities Lorenz force in a the print headmay be high, current carrying wire manufacturing resulting in is used tomove the process electromigration actuator. problems Pulsed A pulsedmagnetic Very low power Complex print IJ10 magnetic field is used tooperation is possible head construction field cyclically attract a Smallprint head Magnetic paddle, which pushes size materials required in onthe ink. A small print head actuator moves a catch, which selectivelyprevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be IJ18, IJ19, IJ20, actuator The expansion may be taken thatthe IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24,IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, othermechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator convertsresulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend Very good High stresses are IJ40, IJ41 bend actuator wherethe two temperature stability involved actuator outside layers are Highspeed, as a Care must be identical. This cancels new drop can be takenthat the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a Better couplingFabrication IJ05, IJ11 spring spring. When the to the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some stackactuators are stacked. Reduced drive fabrication piezoelectric ink jetsThis can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can be used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp 418- into a high travel, Generally high 423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple High energy is Hewlett-Packard expansion actuatorchanges, construction in the typically required to Thermal Ink jetpushing the ink in all case of thermal ink achieve volume CanonBubblejet directions. jet expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in Efficient High fabrication IJ01, IJ02, IJ04, normal toa direction normal to coupling to ink complexity may be IJ07, IJ11, IJ14chip surface the print head surface. drops ejected required to achieveThe nozzle is typically normal to the perpendicular in the line ofsurface motion movement. Parallel to The actuator moves Suitable forFabrication IJ12, IJ13, IJ15, chip surface parallel to the print planarfabrication complexity IJ33, , IJ34, IJ35, head surface. Drop FrictionIJ36 ejection may still be Stiction normal to the surface. Membrane Anactuator with a The effective Fabrication 1982 Howkins push high forcebut small area of the actuator complexity U.S. Pat. No. 4,459,601 areais used to push a becomes the Actuator size stiff membrane that ismembrane area Difficulty of in contact with the ink. integration in aVLSI process Rotary The actuator causes Rotary levers Device IJ05, IJ08,IJ13, the rotation of some may be used to complexity IJ28 element, sucha grill or increase travel May have impeller Small chip area friction ata pivot requirements point Bend The actuator bends A very small Requiresthe 1970 Kyser et al when energized. This change in actuator to be madeU.S. Pat. No. 3,946,398 may be due to dimensions can be from at leasttwo 1973 Stemme differential thermal converted to a large distinctlayers, or to U.S. Pat. No. 3,747,120 expansion, motion. have a thermalIJ03, IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24,expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33,IJ34, other form of relative IJ35 dimensional change. Swivel Theactuator swivels Allows operation Inefficient IJ06 around a centralpivot. where the net linear coupling to the ink This motion is suitableforce on the paddle motion where there are is zero opposite forces Smallchip area applied to opposite requirements sides of the paddle, e.g.Lorenz force. Straighten The actuator is Can be used with Requirescareful IJ26, IJ32 normally bent, and shape memory balance of stressesstraightens when alloys where the to ensure that the energized. austenicphase is quiescent bend is planar accurate Double The actuator bends inOne actuator can Difficult to make IJ36, IJ37, IJ38 bend one directionwhen be used to power the drops ejected by one element is two nozzles.both bend directions energized, and bends Reduced chip identical. theother way when size. A small another element is Not sensitive toefficiency loss energized. ambient temperature compared to equivalentsingle bend actuators. Shear Energizing the Can increase the Not readily1985 Fishbeck actuator causes a shear effective travel of applicable toother U.S. Pat. No. 4,584,590 motion in the actuator piezoelectricactuator material. actuators mechanisms Radial con- The actuatorsqueezes Relatively easy High force 1970 Zoltan U.S. Pat. No. strictionan ink reservoir, to fabricate single required 3,683,212 forcing inkfrom a nozzles from glass Inefficient constricted nozzle. tubing asDifficult to macroscopic integrate with VLSI structures processesCoil/uncoil A coiled actuator Easy to fabricate Difficult to IJ17, IJ21,IJ34, uncoils or coils more as a planar VLSI fabricate for non- IJ35tightly. The motion of process planar devices the free end of the Smallarea Poor out-of-plane actuator ejects the ink. required, thereforestiffness low cost Bow The actuator bows (or Can increase the Maximumtravel IJ16, IJ18, IJ27 buckles) in the middle speed of travel isconstrained when energized. Mechanically High force rigid requiredPush-Pull Two actuators control The structure is Not readily IJ18 ashutter. One actuator pinned at both ends, suitable for ink jets pullsthe shutter, and so has a high out-of- which directly push the otherpushes it. plane rigidity the ink Curl A set of actuators curl Goodfluid flow Design IJ20, IJ42 inwards inwards to reduce the to the regionbehind complexity volume of ink that the actuator they enclose.increases efficiency Curl A set of actuators curl Relatively simpleRelatively large IJ43 outwards outwards, pressurizing construction chiparea ink in a chamber surrounding the actuators, and expelling ink froma nozzle in the chamber. Iris Multiple vanes enclose High efficiencyHigh fabrication IJ22 a volume of ink. These Small chip area complexitysimultaneously rotate, Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates The actuator canLarge area 1993 Hadimioglu vibration at a high frequency. be physicallydistant required for et al, EUP 550,192 from the ink efficient operation1993 Elrod et al, at useful frequencies EUP 572,220 Acoustic couplingand crosstalk Complex drive circuitry Poor control of drop volume andposition None In various ink jet No moving parts Various otherSilverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and doesnot move. required to related patent eliminate moving applications partsTone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way Fabrication Low speed Thermal ink jettension that ink jets are simplicity Surface tension Piezoelectric inkrefilled. After the Operational force relatively jet actuator isenergized, simplicity small compared to IJ01-IJ07, IJ10- it typicallyreturns actuator force IJ14, IJ16, IJ20, rapidly to its normal Longrefill time IJ22-IJ45 position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires IJ08, IJ13, IJ15, oscillatingchamber is provided at Low actuator common ink IJ17, IJ18, IJ19, inkpressure a pressure that energy, as the pressure oscillator IJ21oscillates at twice the actuator need only May not be drop ejection openor close the suitable for frequency. When a shutter, instead ofpigmented inks drop is to be ejected, ejecting the ink drop the shutteris opened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asRequires two IJ09 actuator actuator has ejected a the nozzle isindependent drop a second (refill) actively refilled actuators pernozzle actuator is energized. The refill actuator pushes ink into thenozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and After theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fiils quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate torefill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill Thermal ink jet channel to the nozzlechamber Operational rate Piezoelectric ink is made long and simplicityMay result in a jet relatively narrow, Reduces relatively large chipIJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet Onlypartially back-flow. effective Positive ink The ink is under a Dropselection Requires a Silverbrook, EP pressure positive pressure, so andseparation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes Fast refill timehydrophobizing, or Possible from the nozzle. both) to prevent operationof the This reduces the flooding of the following: IJ01- pressure in thenozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the printhead. IJ14, IJ16, IJ20, required to eject a IJ22, , IJ23-IJ34, certainvolume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure resultsin a reduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is Design HP Thermal Ink are placed in the inletnot as restricted as complexity Jet ink flow. When the the long inletMay increase Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rateIJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow. steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzlehas a substantially May result in a smaller cross section relativelylarge chip than that of the nozzle, area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01, IJ03, IJ05, located problem of inlet back-problem is design to minimize IJ06, IJ07, IJ10, behind the flow byarranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushingink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface theactuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34,IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to Silverbrook, EP actuator ofink jet, there is no problem is ink back-flow on 0771 658 A2 and doesnot expansion or eliminated actuation related patent result in inkmovement of an applications back-flow actuator which may Valve-jet causeink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are No added May not be Most ink jet nozzlefiring fired periodically, complexity on the sufficient to systemsbefore the ink has a print head displace dried ink IJ01, IJ02, IJ03,chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09,IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20,IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26,IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, afterIJ32, IJ33, J334, first moving the print IJ36, IJ37, IJ38, head to acleaning IJ39, IJ40,, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra Insystems which heat Can be highly Requires higher Silverbrook, EP powerto the ink, but do not boil effective if the drive voltage for 0771 658A2 and ink heater it under normal heater is adjacent to clearing relatedpatent situations, nozzle the nozzle May require applications clearingcan be larger drive achieved by over- transistors powering the heaterand boiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used succession rapid succession. In extradrive circuits depends with: IJ01, IJ02, of actuator someconfigurations, on the print head substantially upon IJ03, IJ04, IJ05,pulses this may cause heat Can be readily the configuration of IJ06,IJ07, IJ09, build-up at the nozzle controlled and the ink jet nozzleIJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20,IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations,it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrationsto dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple Notsuitable May be used power to not normally driven to solution wherewhere there is a with: IJ03, IJ09, ink pushing the limit of its motion,applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing maybe actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30,IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41,IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle HighIJ08, IJ13, IJ15, resonance applied to the ink clearing capabilltyimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic blockages. This is actuators easiest toachieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EPclearing plate is pushed against severely clogged mechanical 0771 658 A2and plate the nozzles. The plate nozzles alignment is related patent hasa post for every required applications nozzle. A post moves Moving partsare through each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires May be used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectro- A nozzle plate is Fabrication High Hewlett Packard formedseparately fabricated simplicity temperatures and Thermal Ink jet nickelfrom electroformed pressures are nickel, and bonded to required to bondthe print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., U.S. Pat.No. low cost head 5,208,604 May produce thin burrs at exit holes SiliconA separate nozzle High accuracy is Two part K. Bean, IEEE micro- plateis attainable construction Transactions on machined micromachined fromHigh cost Electron Devices, single crystal silicon, Requires Vol. ED-25,No. 10, and bonded to the precision alignment 1978, pp 1185-1195 printhead wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins etal., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries No expensiveVery small 1970 Zoltan U.S. Pat. No. capillaries are drawn from glassequipment required nozzle sizes are 3,683,212 tubing. This method Simpleto make difficult to form has been used for single nozzles Not suitedfor making individual mass production nozzles, but is difficult to usefor bulk manufacturing of print heads with thousands of nozzles.Monolithic, The nozzle plate is High accuracy Requires Silverbrook, EPsurface deposited as a layer (<1 μm) sacrificial layer 0771 658 A2 andmicro- using standard VLSI Monolithic under the nozzle related patentmachined deposition techniques. Low cost plate to form the applicationsusing VLSI Nozzles are etched in Existing nozzle chamber IJ01, IJ02,IJ04, litho- the nozzle plate using processes can be Surface may beIJ11, IJ12, IJ17, graphic VLSI lithography and used fragile to the touchIJ18, IJ20, IJ22, processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31,IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44Monolithic, The nozzle plate is a High accuracy Requires long IJ03,IJ05, IJ06, etched buried etch stop in the (<1 μm) etch times IJ07,IJ08, IJ09, through wafer. Nozzle Monolithic Requires a IJ10, IJ13,IJ14, substrate chambers are etched in Low cost support wafer IJ15,IJ16, IJ19, the front of the wafer, No differential IJ21, IJ23, IJ25,and the wafer is expansion IJ26 thinned from the back side. Nozzles arethen etched in the etch stop layer. No nozzle Various methods have Nonozzles to Difficult to Ricoh 1995 plate been tried to eliminate becomeclogged control drop Sekiya et al U.S. Pat. No. the nozzles entirely, toposition accurately 5,412,413 prevent nozzle Crosstalk 1993 Hadimiogluclogging. These problems et al EUP 550,192 include thermal bubble 1993Elrod et al mechanisms and EUP 572,220 acoustic lens mechanisms TroughEach drop ejector has Reduced Drop firing IJ35 a trough throughmanufacturing direction is sensitive which a paddle moves. complexity towicking. There is no nozzle Monolithic plate. Nozzle slit Theelimination of No nozzles to Difficult to 1989 Saito et al instead ofnozzle holes and become clogged control drop U.S. Pat. No. 4,799,068individual replacement by a slit position accurately nozzlesencompassing many Crosstalk actuator positions problems reduces nozzleclogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along the Simple Nozzles limited Canon Bubblejet (‘edgesurface of the chip, construction to edge 1979 Endo et al GB shooter’)and ink drops are No silicon High resolution patent 2,007,162 ejectedfrom the chip etching required is difficult Xerox heater-in- edge. Goodheat Fast color pit 1990 Hawkins et sinking via substrate printingrequires al U.S. Pat. No. 4,899,181 Mechanically one print head perTone-jet strong color Ease of chip handing Surface Ink flow is along theNo bulk silicon Maximum ink Hewlett-Packard (‘roof surface of the chip,etching required flow is severely TIJ 1982 Vaught et shooter’) and inkdrops are Silicon can make restricted al U.S. Pat. No. 4,490,728 ejectedfrom the chip an effective heat IJ02, IJ11, IJ12, surface, normal to thesink IJ20, IJ22 plane of the chip. Mechanical strength Through Ink flowis through the High ink flow Requires bulk Silverbrook, EP chip, chip,and ink drops are Suitable for silicon etching 0771 658 A2 and forwardejected from the front pagewidth print related patent (‘up surface ofthe chip. heads applications shooter’) High nozzle IJ04, IJ17, IJ18,packing density IJ24, IJ27-IJ45 therefore low manufacturing cost ThroughInk flow is through the High ink flow Requires wafer IJ01, IJ03, IJ05,chip, chip, and ink drops are Suitable for thinning IJ06, IJ07, IJ08,reverse ejected from the rear pagewidth print Requires special IJ09,IJ10, IJ13, (‘down surface of the chip. heads handling during IJ14,IJ15, IJ16, shooter’) High nozzle manufacture IJ19, IJ21, IJ23, packingdensity IJ25, IJ26 therefore low manufacturing cost Through Ink flow isthrough the Suitable for Pagewidth print Epson Stylus actuator actuator,which is not piezoelectric print heads require Tektronix hot fabricatedas part of heads several thousand melt piezoelectric the same substrateas connections to drive ink jets the drive transistors. circuits Cannotbe manufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink which Environmentally Slow drying Most existing ink dyetypically contains: friendly Corrosive jets water, dye, surfactant, Noodor Bleeds on paper All IJ series ink humectant, and May jets biocide.strikethrough Silverbrook, EP Modern ink dyes have Cockles paper 0771658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol 2- can be used wherethe Operates at sub- Flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a ink jets head beforejetting. Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks aremedium can be used Printed pages U.S. Pat. No. 4,820,346 usually waxbased, No paper cockle may ‘block’ All IJ series ink with a meltingpoint occurs Ink temperature jets around 80° C. After No wicking may beabove the jetting the ink freezes occurs curie point of almost instantlyupon No bleed occurs permanent magnets contacting the print Nostrikethrough Ink heaters medium or a transfer occurs consume powerroller. Long warm-up time Oil Oil based inks are High solubillty Highviscosity: All IJ series ink extensively used in medium for some this isa significant jets offset printing. They dyes limitation for use in haveadvantages in Does not cockle ink jets, which improved paper usuallyrequire a characteristics on Does not wick low viscosity. Some paper(especially no through paper short chain and wicking or cockle).multi-branched oils Oil soluble dies and have a sufficiently pigmentsare required. low viscosity. Slow drying Micro- A microemulsion is aStops ink bleed Viscosity higher All IJ series ink emulsion stable, selfforming High dye than water jets emulsion of oil, water, solubility Costis slightly and surfactant. The Water, oil, and higher than watercharacteristic drop size amphiphilic soluble based ink is less than 100nm, dies can be used High surfactant and is determined by Can stabilizeconcentration the preferred curvature pigment required (around of thesurfactant. suspensions 5%)

I claim:
 1. A method of manufacturing an ink jet printhead, the methodcomprising the steps of: depositing a sacrificial material on asubstrate and etching the sacrificial material to form a plurality ofink chambers on the substrate, with each ink chamber having an inkejection port; and depositing a thermal expansion material and aconductive material, capable of being resistively heated, on thesubstrate so that the conductive material is positioned in the thermalexpansion material; etching the conductive material and the thermalexpansion material to form a thermal actuator having a free end in eachchamber, so that each thermal actuator comprises an electrical heaterelement of the conductive material, positioned in the thermal expansionmaterial, the thermal expansion material having a coefficient of thermalexpansion which is such that the thermal expansion material is capableof expansion upon heating by the electrical heater element, the step ofdepositing the thermal expansion material and the conductive materialbeing carried out so that the heater element is positioned in thethermal expansion material such that expansion of the thermal expansionmaterial results in displacement of the free end of the thermal actuatorwith respect to the ink ejection port.
 2. A method as claimed in claim1, wherein the substrate comprises a silicon wafer.
 3. A method asclaimed in claim 1, wherein the thermal expansion material comprisespolytetrafluoroethylene.
 4. A method as claimed in claim 1, wherein theheater elements comprise copper.
 5. A method as claimed in claim 1,further comprising the step of connecting the heater elements tointegrated drive electronics for providing the heater elements with anelectrical power supply.
 6. A method as claimed in claim 5, furthercomprising the step of forming the integrated drive electronics with aCMOS process.
 7. A method as claimed in claim 1, wherein each thermalactuator is formed with the steps of: depositing a layer of sacrificialmaterial on the substrate; depositing a first layer of the thermalexpansion material; depositing, exposing and developing a gray-scalemask layer on the layer of the thermal expansion material; etching thegray-scale mask layer and the layer of the thermal expansion material,wherein etch rates for the mask material and for the thermal expansionmaterial are substantially the same, so that a corrugated pattern istransferred onto the first layer of the thermal expansion material;depositing a layer of the conductive material onto the corrugated firstlayer of the thermal expansion material; and depositing a second layerof the thermal expansion material on the conductive material so thateach heater element is embedded in the thermal expansion material.
 8. Amethod as claimed in claim 7, further comprising the step of planarizingthe second layer of the thermal expansion material.